The Michigan State Police is opening an internal investigation into a traffic stop that has raised allegations of racial profiling.

The ACLU called on the Michigan State Police to look into the February traffic stop of an American citizen of Mexican descent.

During the traffic stop in Livonia, the ACLU claims the state trooper interrogated about the man about his immigration status, apparently not believing the man’s claims that he is a naturalized citizen.

The driver was handcuffed, threatened with deportation and federal immigration agents were called.

The man was eventually released after his claim of being a legal U.S. citizen was confirmed.

In a written statement, the head of the Michigan State police says the department “expects its members to perform their duties in a professional and impartial manner”, adding the department does not condone “bias profiling”.